Brittle failure caused by lamellar splitting in a large-scale tubular joint with fatigue cracks

This paper reports a new incidence of brittle failure by lamellar splitting in a large-scale tubular X-joint and examines the possible causes of this failure. The X-joint, with multiple pre-existing fatigue cracks at the weld toe along the brace-to-chord intersection, experiences brittle failure during a monotonic in-plane bending test. Post-test sectioning of the material around the brace-to-chord intersection reveals lamellar splitting in the mid-thickness of the chord wall instead of rapid extensions of the fatigue cracks in the through-thickness direction. The lamellar splitting observed in this test differs from the conventional lamellar tearing both in its appearance and in its causes. The elongated nonmetallic inclusions concentrated at the mid-thickness, as revealed by the microscopic scanning, leads to delamination cracking near the mid-thickness and subsequently to the brittle failure of the joint. The material requirements in prevailing engineering codes do not suffice to prohibit the lamellar splitting failure observed in this study, which may cause catastrophic failures in engineering structures designed with insufficient redundancy.     

67CrVA弹簧钢在斯太尔发动机气门弹簧上的应用试验

针对由67CrVA弹簧钢制造的斯太尔发动机气门弹簧进行了各项性能试验，结果表明，气门弹簧经合适的喷丸强化、热强压工艺处理后，其疲劳寿命、负荷损失率均达到标准要求；松弛试验结果表明，67CrVA弹簧钢是一种具有良好的抗松弛性能和疲劳性能的材料。最后进行了装机试验，经l000h台架试验，67CrVA弹簧钢制造的斯太尔发动机气门弹簧性能指标达到了QZZ1ll8—1994标准的要求。     

人体慢性吗啡依赖对内分泌的影响

采用放射免疫法对３０例慢性吗啡依赖者进行了治疗前、后血中皮质醇（ｃｏｒｔｉ－ｓｏｎ,ＣＯＲ）及生长激素（ｇｒｏｗｔｈｈｏｒｍｏｎｅ,ＧＨ）水平的测定,并以３０例健康人作对照。结果表明：人体慢性吗啡依赖者体内ＣＯＲ、ＧＨ水平显著升高,经一个月的戒毒治疗后体内ＣＯＲ、ＧＨ水平下降,但仍高于正常,此时临床上观察到吗啡依赖者躯体戒断症状全部消失,说明内分泌激素ＣＯＲ、ＧＨ参与慢性吗啡依赖的形成。     

试论商品质量规律和商品价值规律

本文在分别解释了商品质量规律和商品价值规律的基础上,论述了它们之间接关系,并着重分析了它们对市场经济的作用,从而得出了它们是市场经济的基本规律的结论。     

拱塔斜拉桥合理索力优化计算分析

文章以某预应力混凝土拱塔斜拉桥为研究对象,通过建立全桥空间有限元模型,利用弯曲能量最小法、影响矩阵法、综合法以及正装迭代改进法对该桥成桥使用阶段和施工阶段的拉索索力进行了优化计算分析。结果表明,采用综合法和正装迭代改进法能有效确定桥梁成桥使用阶段和施工阶段的合理拉索索力。     

A COMPREHENSIVE EVALUATION OF THE ROLE OF INHERITANCE AND ENVIRONMENTAL FACTORS IN PRIMARY LIVER CANCER

ＡＣＯＭＰＲＥＨＥＮＳＩＶＥＥＶＡＬＵＡＴＩＯＮＯＦＴＨＥＲＯＬＥＯＦＩＮＨＥＲＩＴＡＮＣＥＡＮＤＥＮＶＩＲＯＮＭＥＮＴＡＬＦＡＣＴＯＲＳＩＮＰＲＩＭＡＲＹＬＩＶＥＲＣＡＮＣＥＲＷａｎｇＸｕｅｌｉａｎｇ；ＸｕＨｕｉｗｅｎ；ＣｈｅｎｇＢｉｎｇ；ＭｅｎＢ...     

雷达图像与电子海图的实时匹配算法及其计算机实现

本文针对已抽取海岸边缘特征并二值化的电子海图和已进行任意实数倍缩小变换至海图比累积误差代替门限序列的粗精搜索间隔采样快速实时匹配。通过计算机仿真，证明该算法简便易行、精度较高、实时性好。     

8K型机车监控装置双机备用系统

分析了8K型机车监控装置双主机和显示器的使用及存在的一些问题,并针对这些问题可能造成的隐患提出了解决的方案。指出了使用单片机智能化设计,以保证系统工作稳定可靠。同时给出了方案的整体试验结果和结论。     

Simulation of the oil spill processes in the Sea of Japan with regional ocean circulation model

A simulation of the movement of spilled oil after the incident of the Russian tanker Nakhodka in the Sea of Japan, in January 1997, was performed by a particle tracking model incorporating advection by currents, random diffusion, the buoyancy effect, the parameterization of oil evaporation, biodegradation, and beaching. The currents advecting spilled oil were defined by surface wind drift superposed on the three-dimensional ocean currents obtained by the Geophysical Fluid Dynamics Laboratory modular ocean model (GFDL MOM), which was forced by the climatological monthly mean meteorological data, or by the European Center for Medium Range Weather Forecasts (ECMWF) daily meteorological data, and assimilated sea surface topography detected by satellite altimeter. A number of experiments with different parameters and situations showed that the wide geographical spread of oil observed is not explained by wind drift alone, and that including the simulated climatological currents gives better results. The combination of surface wind drift and daily ocean currents shows the best agreement between the model and observations except in some coastal areas. The daily meteorological effect on the ocean circulation model results in a stronger variability of currents that closely simulates some features of the nonlinear large-scale horizontal turbulent diffusion of oil. The effect of different parameterizations for the size distribution of model oil particles is discussed. Received for publication on July 26, 1999; accepted on Nov. 17, 1999     

On nonlinear ship waves and wave resistance calculations

A finite difference method based on the Euler equations is developed for computing ship waves and wave resistances. Time marching is carried out using a time-splitting fractional-step method. The second-order central difference is used to discretize the spatial differentials, while the convection terms are discretized by the QUICK scheme. A body- and free-surface-fitted grid system with a cell-centered stencil is used. A Poisson equation for the pressure increment at each time step is solved to enforce mass conservation. The method is validated by comparing the numerical results with the experimental data for a Wigley parabolic hull. The characteristics of ship waves, such as the wave profile along the hull, the wave pattern on the free surface, the pressure distribution on the hull surface, and the wave-making resistance are reasonably predicted. The calculated results are in good agreement with the experimental data. Received for publication on Oct. 13, 1998; accepted on Jan. 20, 1999